The present invention is directed to a heat shield, and more particularly to a heat shield for use in a vehicle with an internal combustion engine, such as an automobile or truck. The present invention is also directed to a method for making such a heat shield.
Modern internal combustion engines are typically designed to have high working temperatures in order to provide high thermodynamic efficiency. The high thermodynamic efficiency reduces fuel consumption, but the high working temperatures of the engine are a source of great practical difficulty in construction and operation of the vehicle. The maximum temperature of combustion of gasoline in a cylinder approaches the melting point of platinum, and even the exhaust gas from an engine may have a temperature above the melting point of aluminum. Careful heat management is necessary to ensure that the components of an automobile can endure long years of reliable use in a high-temperature environment.
Heat shields are used increasingly in modern automobiles as a technique for managing heat. Since the heat management problems typically vary from one automobile model to the next, depending upon a number of factors such as engine horsepower and design, the layout of components under the hood, susceptibility of various components to deterioration due to high temperature, underhood airflow, and so forth, the exact configuration of the heat shields that are needed for optimum automotive performance will also vary from model to model.
For several years the assignee of the present application has sold manifold heat shields for preventing vapor lock by shielding gasoline conduits from engine heat, thereby reducing the chance that the gasoline might vaporize before reaching the fuel injectors. The manifold heat shield included a wrapper member stamped from sheet metal. The wrapper member had a cover portion and flanges extending from the cover portion. The flanges were bent to form a tray. A ceramic fiber insulation member was deposited in the tray without adhesive. The ceramic fiber insulation member was stamped from sheet material and had a shape congruent to the shape of the cover portion of the wrapper member. The manifold heat shield also included an outer member stamped from sheet metal and having a shape congruent to the shape of the cover portion of the wrapper member. The outer member was stacked without adhesive on top of the ceramic fiber insulation member and the flanges extending from the cover member were then folded over to press against the outer member along the periphery thereof. This formed a flat intermediate product.
The intermediate product was then bent at several places, using one or more stamping presses equipped with forming dies, to achieve the desired configuration for the manifold heat shield. Since each bend changed the shape and effective length of the workpiece as the respective bend was formed, separate die sets and ram strokes were employed for each bend. Although the workpiece could be moved from one press to another as the separate bends were formed, a single press with the necessary dies could be employed if the workpiece itself were moved from position to position between ram strokes.
After all the bends were formed in the workpiece, the manifold heat shield was completed by clipping hardware onto the bent workpiece. The completed manifold heat shield could then be installed in an automobile by bolting the hardware to the engine.
While the above-described manifold heat shield reduced the risk of vapor lock, experience has shown that the heat shield was insufficiently rugged for use in demanding applications. Relatively thick sheet metal was needed for the wrapper member in order to avoid deformations, and the clip-on mounting hardware did not secure the heat shield with the reliability that was desired. Moreover, forming the desired bends in the manifold heat shield was relatively labor-intensive and thus expensive.